Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper or foil and coat it with nonstick spray to ensure easy removal of the bars later. Set the prepared pan aside while you make the batter.

In the bowl of a stand mixer fitted with the paddle attachment, combine the unsalted butter and light brown sugar. Mix on medium speed for about 2 minutes, until well incorporated. Add the eggs, vanilla extract, baking powder, and kosher salt; mix for another minute, scraping the sides of the bowl as needed, until the mixture is smooth.

Turn the mixer to low speed and add in the flour. Mix just until incorporated, being careful not to overmix. Using a spatula or the mixer on its lowest setting, stir in the chopped dried cranberries, chopped pistachios, and white chocolate chips until evenly distributed throughout the dough. I find folding these in by hand helps keep the mix-ins from breaking up too much.

Spread the blondie batter evenly into the prepared pan. Bake in the preheated oven for 18-20 minutes, or until the center is just set—don’t over-bake to ensure a chewy texture. Allow the bars to cool completely in the pan before adding any frosting or toppings.

Once the bars are fully cooled, beat the cream cheese and confectioners' sugar together in the bowl of your stand mixer, using the paddle attachment, until the mixture is smooth and creamy. Spread this frosting evenly over the cooled bars. For a smoother finish, I like to chill the bars slightly before frosting.

Sprinkle the frosted bars with extra chopped dried cranberries and chopped pistachios as desired. Drizzle with the melted white chocolate chips for an extra touch of sweetness and visual appeal. Let the white chocolate set before cutting the bars into squares or rectangles. These make a beautiful holiday treat!